Cell-free activation of a DNA-binding protein by epidermal growth factor

Abstract

GROWTH factors such as platelet-derived growth factor and epidermal growth factor (EGF) bind to and activate cell-surface receptors with intrinsic tyrosine kinase activities¹. Receptor activation elicits multiple physiological changes in target cells, including alterations in gene expression^2–4. Receptor tyrosine kinase signalling involves recruitment of proteins into a signalling complex through interactions between receptor autophosphorylation sites and the src-homology region-2 (SH2) domains on these signalling proteins^5–9. Diverse signals can subsequently be generated, depending on the specific receptor and cell type^2,10. How such signals are transmitted to the nucleus is poorly understood, but because the transcriptional activation of many genes by growth factors occurs in the absence of new protein synthesis⁴, one or more signals emanating from growth factor receptors must directly affect transcription factors. We report here the activation by EGF of a DNA-binding protein in a cell-free system where activation of DNA binding requires ligand, receptor, ATP and phosphotyrosine–SH2 interactions.